Pressure balanced vane



Sept. 3, 1963 J. DAVIN 3,102,493

PRESSURE BALANCED VANE Filed Feb. 10, 1961 3 Sheets-Sheet 1 INVENTOR.

JOSEPH DAV/N B I Y OLSON 8 TREXLER Sept. 3, 1963 J. DAVIN PRESSURE BALANCED VANE 3 Sheets-Sheet 2 Filed Feb. 10, 1961 INVEN JOSEPH 0 BY OLSON a TREXLER" Sept. 3, 1963 J. DAVIN 3,102,493

PRESSURE BALANCED VANE FiledFeb. 10, 1961 3 Sheets-Sheet 3 INVENT OR. JOSEPH DAV/N BY OLSON 8 TREXLER United States Patent M 3,102,493 PRESSURE BALANCED VANE Joseph Davin, Weston, Mass, assignor to American Brake Shoe Company, New York, NY, a c'orporation of Delaware Filed Feb. 10, 1961, Ser. No. 88,331 Claims. (Cl. 103-135) The present invention is directed a vane pumps and motors in which a plurality of circumferentially spaced vanes are sl-idably mounted in spaced slots in a rotor for sealing engagement with an encircling cam or cam surface. For convenience in description, reference will be 'made in this application primarily to vane pumps with the understanding that the invention is not necessarily limited to pumps but is also applicable to vane motors, the term hydraulic power unit being used to designate either-a pump or a motor. t i

One object of the invention is to provide an improved vane pump or motor in which the force of fluid pressure on each vane tending to force the low pressure side of the vane against the opposing side surface of the coacting rotor slot is balanced by opposing force of fluid pressure on the vane to the end that the vane is virtually free of frictional restraint against sliding movement in its slot, even though the fluid pressure in the interspace between the rotor and cam at one side of the vanegreatly exceeds the fluid pressure in the interspace between the rotor and cam at the opposite side of the vane.

Another object is to provide animproved vane pump or motor in which the maximum force of fluid pressure tending to force each vane againstthe rotor structure defining the coacting vane slots is limited to that necessary for forming an effective seal between the vane and rotor.

Another object is to provide .a vane pump or motor unit having an improved construction which minimizes to great advantage the forces required to move the vanes in the coacting rotor slots to maintain continuous engagement of the individual vanes with the encircling cam, while at the same time prolonging the surface life of the unit by minimizing wear on the vanes, rotor, and cam.

Another object is to provide an improved vane pump or motor in which the reaction of fluid on the rotor is applied to the rotor almost entirely by fluid pressure acting directly on the rotor, thereby substantially obviating any necessity for transmitting the forces of the fluid reaction to the rotor through mechanical pressure engagement of the vanes with the rotor.

Another object is to provide a vane pump or motor unit having an improved construction which maintains a substantially complete balancing against each other of the forces of fluid pres-sure acting on each vane in a direction perpendicular to the central plane of the coacting vane slot, while at the same time maintaining an effective seal against the escape of fluid past each'vane between the interspaces between the rotor and cam at opposite sides of the vane.

A further object is to provide an improved vane pump or motor unit having a service life which is greatly extended by virtue of an improved construction of the unit which substantially eliminates frictional resistance to movement of the vanes in the coacting rotor slots and serves to maintain an adequate but not excessive sealing pressure between the individual vanes and the coacting cam.

A further object is to achieve the objects previousl recited in an improved vane pump or motor unit which is adapted for adjustment of the displacement of the unit.

Other objects and advantages will become. apparent Patented Sept. 3, 1963 from the following description of the exemplary embodiment of the invention illustrated in the drawings, in which:

FIGURE 1 is a simplified transverse sectional view of a vane pump embodying the invention;

FIG. 2 is an enlarged transverse sectional view of a vane pump illustrating principles of the invention in somewhat schematic form;

FIG. 3 is a fragmentary sectional view of the pump corresponding to FIG. 2, but showing in substantial detail the actual construction of a preferred form of vane used in the pump illustrated;

FIG. 4 is a view similar to FIG. 3 drawn on a somewhat reduced scale, and illustrating the vane in longitudinal section, the vane in both FIGS. 3 and 4 being shown in its extended position;

FIG. 5 ha view similar'to FIG. 4, but showing the vane in its retracted position;

FIG. .6 is a distal side view of the vane, taken with reference to the line6-6 of FIG. .4; and

FIG. 7 is a longitudinal sectional view of the vane, taken with reference to the line 77 of FIG. 5.

Referring to the drawings in greater detail, the hydraulic power unit 10 forming the exemplary embodiment of the invention illustrated is designed to function as a pump and comprises a cylindrical rotor 12 supported and driven in the clockwise direction with reference to FIG. 1 by a shaft 14. The rotor 12 rotates within an annular cam 16 defining a cam surface 18 which encircles the cylindrical surface 20 of the rotor. v

The pump 10 illustrated is designed to be a balanced pump. For this reason, the cam surface 18 is shaped in relation to the rotor surface 20 to define therebetween twojinterspaces located generally on diametrically opposite sides of the rotor 12, and designated in FIG. 1 by the numbers 22, 24. Two fluid inlet ports 26, 28 communicate with the inlet ends of the respective interspaces 22, 24, as indicated schematically in FIG. 1. Since the rotor 12 turns in the clockwise direction, the inlet ports 26, 28 communicate with the counterclockwise ends of the spaces 22, 24. Fluid entering the spaces 22, 24 through the inlet ports 26;28 is discharged through outlet ports 30, 32 communicating with the opposite or outlet ends of the pumping spaces.

Fluid is pumped through the spaces 22, 24 between the connecting inlet and outlet ports by a plurality of circumferentially spaced vanes 34 slidably mounted in a corresponding series of slots 36, formed in the rotor. Eachvane 34 has a generally rectilinear over-all form" andiis dimensioned to have a close sliding jfi't within its coacting slot 36, which permits the vane to move within the slot to continuously engage the encircling cam surface 18. M

Opposite ends of the rotor 12 are engaged by conventional cheek plates orsi'milar conventional pump com ponents (not shown.) which enclose opposite sides of the interspaces 22, 24, andhave a close sliding fit with opposite ends'of' the rotor and with corresponding edge surfaces of the vanes. The relationship of the cheek plates, or similar structure, to the rotor and vanes is conventional and will be well understood by those skilled in the art without further description here.

As shown, the individual vane slots 36 in the rotor 12 are turned at an acute angle with reference to radial lines through the respectiveslots. The angle to which a typical slot 36 is turned with reference to a radial line 38 through the outlet ends of the slot is identified in PEG. 2 by the number 40. V

As shown in greater detail in FIG. 2, each slot 36 comprises two parallel side surfaces 42, 44 parallel to the axis of the rotor 12 and disposed in opposed sliding vane 34. Because of the angular inclination of each slot with respect to a radial line through the slot, as indicated by the angle 40 in FIG. 2,,the sides 42 and 44 of the slots and the corresponding sides of the coacting vane have a'distal and proximal relationship respectively to the axis of the rotor 12.

As each vane 34 enters one of the pumping spaces 22, 24" it forms a partition separating that portion of the interspace ahead of the vane from that portion of the interspace located behind the vane. For convenience in description with reference to FIGS. 2 to 5, that portion of the interspace 22 located immediately ahead of any particular vane 34 is identified by the number 2211, and the portion of the interspace located immediately behind th vaneis identified by the number 22b.

Movement of the vanes 34 through the pumping interspace 22, for example, creates pressure differentials across the varies in which the pressure in the interspaces 22a immediately ahead of the vanes exceeds the pressure in the interspaces 22b behind the vanes.

The differential pressures across the vanes 34 passing through the pumping spaces 22, 24 tend to produce a torque reaction on the rotor 12. In a pump this torque reaction is overcome by the driving force of the shaft 14. In a motor the torque reaction of differential fluid pressure forces on the vanes tend to produce output torque.

In the pump disclosed, a fluid pressure in the pumping, space 22a immediately ahead of a vane 34 which exceeds the fluid pressure in the space 22b immediately behind the vane, FIG. 2, tends to force the proximal side 46 of the vane laterally against the opposing proximal side 44" of the coacting vane slot. This urging of the vane against the proximal side of the coacting vane slot, due to differential pressure in the pumping spaces 22a, 22b adjacent the vane, tends to produce between the vane and its coacting slot a frictional resistance to radial movement of the vane within the slot. Such friction between a typical vane, and its slot tends to cause wear of bot-h the vane and slot and imposes a drag on movement of the vane, with a corresponding increase in the force necessary'to move the vane radially within its slot to maintain engagement of the vane With the cam surface 18.

In a hydraulic power unit constructed in accordance with this invention, the torque reaction on the rotor due to dififer'ential fluid pressures existing across the vanes in the rotor is transmitted to the rotor primarily by fluid pressure, rather than by forces transmitted mechanically between the vanes and the rotor, this action being accompanied by a substantial balancing of the forces of fluid pressure tending to force the vanes laterally into engagement with the opposing slot surfaces, and by a reduction of the mechanical pressure engagement of each vane with its coacting slot to that which is necessary to form an efiective seal between the vane and the rotor.

Having reference to FIG. 2, in which principles of the invention are illustrated somewhat schematically, a typical vane 34 moving through the, typical pumping space 22, is urged toward the proximalside surface 44 of the coacting slot 36 when the pressure in the interspace 22a immediately. ahead of the vane exceeds the pressure in the interspace 22b immediately behind the vane. This force of differential fluid pressure tending to urge the vane 7 against the low pressure side of the slot is largely balanced or offset by opposing forces of fluid pressure which reduce the pressure engagement of thevane with the side surface 44 to that required for forming an eifective seal against the escape of fluid around the vane through the slot.

-For this purpose, the typical vane 34 is shaped in relation to the coacting slot 36 to define between the proxi rnal side 46 of the vane and the proximal side 44 of the slot a balancing interspace 50 which is isolated from the pumping interspace 22b adjacent the low pressure side of the vane, while at the same time being connected to the interspace 22a adjacent the high pressure side of the vane. Thus, the balancing interspace 50 is continuously maintained under the same fluid pressure as the pumping interspace 22a at the high pressure side of the vane. The pressure of the fluid within the interspace 5i acts on the proximal or low pressure side of the vane to produce a lateral force on the vane which tends to offset the previously described force of fluid pressure tending to urge the vane into frictional engagement with the low pressure side 44 of the coacting vane slot.

Referring to the drawings in greater detail, it will be noted with reference to the simplified illustration of a typical vane 34 in FIG. 2, that the balancing interspace 50 is defined by the proximal side 44 of the coacting slot and by a cavity 52 recessed into the proximal side of the vane. The interspace 50 thus formed is isolated from communication with the bottom of the coacting slot by engagement with the proximal side surface 44 of an inner sealing surface 54 formed on the proximal side of the vane between the recess 52 and the inner extremity of the vane. Similarly, the balancing interspace 50 is isolated from communication with the interspace 22b between the cam and rotor adjacent the low pressure side of the vane, by structure which includes an outer sealing surface 56 formed on the proximal side of the vane between the cavity 52 and the outer extremity of the vane and slidably engaging the proximal slot surface 44.

A transverse bore or cavity 58 formed in a typical vane 34 provides a passage connecting the balancing interspace 50, FIG. 2, on the low pressure side of the vane with a cavity 60 recessed into the opposite side of the vane and confronting the distal side. 42 of the vane slot. When the vane is extended as illustrated in FIG. 2, the cavity 60 communicates directly with the pumping interspace 22a at the high pressure side of the vane. When the vane is retracted, the cavity 60 continues to communicate with the interspace 22a through a recess 62 formed in the I outer end of the distal side of the vane slot, thus providing the desired uninterrupted communication of the interspace 22a with the balancing interspaceStl. The cavity 60 is isolated from communication with the bottom of the coacting vane slot by sliding engagement with the distal side surface 42 of the slot of a. sealing surface 64 formed on the distal side of the vane between the cavity 60 and the radially inward extremity of the vane. 1

It will be'appreciated that the cavity 60 in the distal side of a typical vane is continuously maintained under the same fluid pressure as that prevailing in the opposed balancing interspace 50' and the adjacent pumping interspace 22a. Outward movement of a vane 34 in its slot causes a portion of the distal cavity 60 to project beyond the rotor 12, as illustrated in FIG. 2. However, projection of the cavity 50 beyond the rotor does not increase the exposure of the distal side of the vane to the pressure within the interspace 22a, since the cavity 60 is continuously connected with the interspace 22a, as described. v

As previously mentioned, the fluid pressure within the balancing interspace 50 operates to offset the lateral force of fluid pressure tending to force the vane against the proximal side surface of the slot when the vane is extended. When the vane is retracted, however, pressure Within the balancing interspace 50 continues to act on the vane to urge it away from the proximal side surface of the coacting slot, even though the vane may not project beyond the slot. At this time, the pressure force within the interspace 50 tending to urge the vane away from the proximal'side of the slot is opposed by the force of the same fluid pressure within the distal cavity 60.

As will'presently appear, with reference to the ensuing description of the actual structure of a typical vane, illustrated in FIGS. 3 to 7, the shaping of each vane is worked slot are substantially balanced against each other at all times.

, The bottom of each vane slot 36 is connected to com- Ymunicatewith the pumping interspace 22b adjacent the proach a balancing of the fluid pressure forces on a vane in a direction parallel to the opposing slot surfaces 42, 44 described. In general, this balancing of fluid pressure forces tending to move a vane radially within its slot simplifies the matter of achieving optimum radial movement of the vane to maintain sealing engagement with the opposing cam surface 18, as will presently appear.

Moreover, as will be described With reference to FIGS. ,4 to 7, the balancing of opposing pressure forces on a typical vane is correlated with other features designed to apply to the vane optimum actuating forces for moving the vane in its slot.

Having reference to FIGS. 3 to 7, which illustrate an 1 actual vane used in the pump 10, it Will be noted that a typical vane 34 issubstantially squared off or truncated at its outer extremity, and is shaped to define on its radially outer extremity a cam sealing edge "76 located adjacent the distal side of the vane and adapted to engage and continuously seal against the cam surface 18. The cam sealing edge7t} on the vane is parallel to the axis of the rotorand is shaped to engage only a very narrow portion of the cam surface 18, the narrowness of the mutually engagedareas of the vane and cam surface approaching line contact of the vane and cam.

Each vane 34 has a very substantial thickness which .is correlated with-the previously described angular inclination of the vane with reference to a radial line through the vane slot so that, upon extension of the vane from its slot, as the vane moves through one of the pumping spaces 22, 24, the cam sealing edge 70 at the distal side of the vane projects a substantial distance beyond the rotor to follow the cam surface 18 tvhile the proximal side of the vane remains within the vane slot, so as not to project beyond the proximal slot surface 44.

It is fitting to point out that the degree to which the distal side of a vane can be extended beyond the rotor while the proximal side of the vane remains within the coaoting rotor slot can be increased by increasing the thickness of the vane. For a vane of a given thickness, the degree to which the distal side ofthe vane can be extended beyondthe rotor, while the proximal side of the vane remains within the coacting slot, canbe, increased by increasing the angle 40, FIG. 2, of the inclination of the vane slot with reference to a radial line 38.

.Put another way, the degree to which the distal side of a vane can be extended under the limitations recited can be increased by increasing in a rotor of a given size the spacing, identified in FIG. 2 by the letter between the medial plane of the vane and the axis of the rotor.

it will be appreciated, with reference to FIG. 3, that the pressure in the interspace 22a adjacent the high pressure side of a typical vane 34 acts on the distal side of the vane all the way out to thesealing edge.70 on the vane which engages the cam surface 18'. Since the sealing edge 70 is located adjacent the outer extremity of the vane, the pressure forces on the vane, which tend to urge the vane against the proximal slot surface 44, extend all the Way out substantially to the end of the vane. To provide the most effective offsetting of these, forces of fluid pressure tending to urge the vane toward the slot surface 44, a typical vane 34 is shaped so that the half ancing interspace 56 on the proximal'side of the vane is located-directly opposite from the area of the distal side of the vane exposed to the pressure within the interspace 22a. Thus, the vane cavity 52, coacting with the slot surface 44 to define the balancing interspace 50, is located along the longitudinal extent of the vane, so that the outermost extremity of the cavity 52 stops only slightly short of the cam sealing edge 70 with respect to the longitudinal medial plane or length of the vane. Put another Way, the cam sealing edge 70 is located with respect to the radially inward extremity of the vane only slightly beyond the outermost portion of the balancing interspace 50.

As shown in FIG. 3, the proximal side of a typical vane 34 does not extend beyond the proximal side 44 of the coacting slot when the vane is fully extended. Extension of the distal side of the'vane beyond the periphery of the rotor 12 While the proximal side of the vane is confined within the vane slot is made possible by the relationship of the thickness of the vane to the angular position of the vane slot relative to a radial line through the center of the vane slot. The position of the balancing cavity 52 on the vane is such that the orthographic projection on the plane of the distal side of the vane of the face of the cavity '52, which confronts the proximal slot surface 49, extends substantially beyond the distal side surface '42 of the coacting slot and into closely adjacent relation to the cam sealing edge 70 on the vane.

the vane in a direction perpendicular to the proximal slot surface 44. Yet, at the same time, the fact that the sealing edge 70 does lie slightly beyond the outer extremity of the balancing interspace 50 with respect to the longitudinal plane of the vane, providesa corresponding differential fluid pressure force on the outer end of the vane which tends to urge the sealing surface 56 on the proximal side of the vane into effective sealing engagement with the proximal slot surface 44. The force or pressure with which the sealing surface 56 is urged against the slot surface 44 is limited to an optimum value for. sealing purposes by the controlled degree to which thesealing edge 70 is located beyond the balancing interspace 50.

It will be understood that the pressure force required to hold the sealing surface 56 in effective sealing engagement with the slot surface 4 4 is only a very small fraction of the total pressure force on the distal side of the vane tending to urge the vane toward the surface 44.

V As shown in FIG. 7,the balancing interspace 50' is connected through three transverse bores 58 with the distal side of the vane exposed to pressure within the interspace 22a; Hence, engagement of the sealing surface 56 with the proximal slot surface 44 is relied onas a seal between the pumping spaces 22a, 2% on opposite sides of the vane. The effectiveness of this seal is increased by widening of the seal 56, while at the same time maintaining the previously described positional relationship along the wane of the cam sealing edge 70 and the balancing interspace 50. It will be understood that both the balancing interspace 50 and the sealing surface 56 extend across the full Width of the vane. I

Widening of the sealing surface 56 to increase its effectiveness is achieved by extending the outer end of the vane somewhat at the side of the vane adjacent the proximal slot surface 44, as shown. This is achieved by forming a step 72 in the outer end of the vane, so that the proximal side of the vane defining the surface 56 extends beyond the distal side of the vane defining the cam sealing edge79 by a slight distance, indicated gena 7 erally by the number 74 in 'FIG. 3. While the step 72 is somewhat abrupt, as illustrated in the drawings, it

:length of the vane .of the cam sealing edge 70 beyond the balancing interspace 50.

The sealing surface 56, even though extended, as described, to improve its sealing effectiveness, is nevertheless limited to the width required for sealing purposes, in

order to maximize the degree to which the cam sealing edge 70 can be extended beyond the rotor while maintaining full engagement of the sealing surface 56 with the slot surface 44.

In moving trom one of the pumping zones or spaces 22, 24, each vane-34' is retracted within its slot 36, as

.indicatedin FIG. 5. Since the rotor 12 has a close fit with thecam surface -18 in the sealing zone between the punipingspaces 22, 24, each vane moving through one of these sealing zones is substantially fully contained within its coasting slot 36; Hence, the ends of the transverse bores 58 opening outwardly through the distal side of a retracted vane are disposed-inwardly of the outer extremity of the distal side surface of the vane slot, as shown inFIG. 5. However, a relief or recess 62, FIGS. ,4 and 5, formed in the distal side 42 of the coacting slot near the outer end of the slot, and previously referred to inithe description having reference to FIG. 2, provides communication between the central one of the transverse vane bores 58 and the interface between the cam surface and rotor at the distal side of the vane, even when the vane is in its fully retracted position described. This assures continued maintenance of the desired balancing of the lateral forces of fluid pressure on the retracted vanes.

As illustrated in FIGS. 3 and 6, the ends of the transverse bores 58 opening outwardly through the distal side of each vane communicate with reliefs orrecesses 80 formed in the distal sides of the vanes inwardly of the cam sealing edge 70. The positional relationships of thecavities 80 to the cavity 52 are such that the orthographic projections of the cavities 80 onto the plane of the distal side of the vane extensively overlap (and, in this instance, lie within) the orthographic projectionof the cavity 52 on the same plane. When a vane is in its retracted position illustrated in FIG. 5, the cavities 80 oppose the distal side of the coacting slot to effect an offsetting of the lateral forceof fluid pressure within the opposed balancing interspace 50.

As shown in FIGS. 3, 6 and 7, the balancing interspace 50 is connected to communicate with the opposite portion of the distal side of the vane, not only by pas-' sages formed bythe transverse bores=58 previously men: tioned, but by passages formed by transverse reliefs or grooves 82 formed in the opposite side edges of the vane in alinernent the cavity 50. It will be understood that the two recesses or channels 8-2 in opposite side edges of each vane are opposed by the previously mentioned pump structure (not shown) which tits against opposite ends of the rotor 12, as described.

It is also noteworthy with respect to FIG. 3, that the inner sealing surfaces 54, 64 formed on the proximal and low pressure side of the vane through four vane bores 66, FIGS. 6 and 7.

Because of the substantial balancing of the forces of fluid pressure on-each vane 34 achieved in the manner described, further advantages are achieved in the provision for actuating each vane in its slot to maintain engagement of the cam sealing edge 7 t] on the vane with the encircling cam surface 18. Each vane is urged outwardly by centrifugal force. Because of the substantial balancing of the forces of fluid pressure on thevane, this may be sufficient in some instances to maintain engagement of the vane with the encircling cam surface. I

Provision is made, in the pump 10 forming the exemplary embodiment of the invention illustrated, for moving the vanes 34 outwardly by fluid pressure which exerts optimum actuating forces on the vanes. For this purpose, each vane is formed to define an actuating surface which, when subjected to fluid pressure, will urge the vane outwardly. Moreover, provisionis made for subjecting this actuating surface to a fluid pressure which is at least equal to the pressure within the interspace between the rotor and cam surface adjacent the high pressure side of the vane.

Having reference to FIGS. 3 to 7, a cylindrical bore '86 is formed in each vane, to open inwardly through the bottom of the vane toward the bottom of the coacting slot 36. A cylindrical plunger 88 is fitted into the bore 86 of each vane, and abuts against the bottom of the coacting slot 36, as shown.

, The bore 86 in each vane communicates with the central transverse bore 58, as shown inFIGS, 3 and 4, whereby the space Within the bore 8-6 at the outer end of the plunger 88 is continuously subjected to the fluid pressure prevailing in the interpace 22a adjacent the high pressure side o-f'the vane. The plunger 88 seals the space within the outer end of the bore 86 from communication with the bottom of the slot 36.

When a vane 34 is moving through the pumping space 22, for example, the pressure in the space 22a ahead of the vane normally exceeds the pressure in the interspace 22b behind the vane. the vane is subjected to a lower pressure thanthe pressure of the fluid within the outer end of the bore 86. Thus, the higher pressure within the outer end of the vane bore 8 6 acts on an actuating area of the vane, to

urge the vane outwardly by a force which is opposed distal sides of the vane to seal against the side surfaces 44, 42, as described, have an extensive longitudinal extent along the radial length of the vane, i.e., that dimension of the vane which extends from its radial inner end to its radial outer end. The extensiveness of the inner sealing areas 54, 56, provides a highly effective sealing of the balancing interspace 50 .and the interspace 22a against communication with the bottom of the coasting slot 36 which is connected to the interspace 22b at the only. by a lower pressure at the outer end of the vane acting on a corresponding end area of the vane. The net result is a differential fluid pressure force tending to urge the vane outwardly with only that degree of force desired for maintaining sealing engagement of the sealing edge 70 with the cam surface 18.

It should be made clear that the transverse sectional area of the bore 86 or each vane is quite small in relation to the corresponding transverse sectional area of the vane. Hence, the plunger 88 does not substantially reduce the efiective area on the inner end of the vane which is exposed to the fluid pressure in the bottom of the coacting slot 36, and which constitutes a balancing area on which fluid pressure effectively balances the fluid pressure on the outer end of the vane, as previously described.

For simplicity in description, it has been assumed generallyin the previous description that, in the pump 10, the pressure in the interspace between the rotor and cam surface ahead of the vane exceeded the pressure in the rotor cam interspace behind the v ane. While this is true during movement of a vane between an inlet port and an outlet port in the pump, this pressure relationship does not prevail during movement of a vane through one of the sealing zones between the outlet ports and the inlet ports. Thus, as a vane moves from the pumping space 22 to the pumping space 2.4, for example, the vane is in its retracted position, illustrated in FIG. 5; Since the Hence, the radially outer end of.

pressure at the outlet port 3tl exceeds the pressure at the inlet port 28, the rotor cam interspace pressure ad acent the trailing side of the vane tends to exceed the pressure in the rotor cam interspace adjacent the leading side of the vane. The efifect of this is to tend to move the vane plunger 88 further into the coacting bore 86. However, movement of the plunger 88 into its bore 86 is limited by a shoulder 90 formed at the bottom of the bore and encircling a connecting aperture 92 communicating with the central transverse bore 58, as shown in FIG. 4.

Thus, when a vane is moving in its retracted position between an outlet and an inlet port of the pump, the pressure on the difierential actuating area of the vane, which opposes the vane plunger, does not exceed the pressure at the outer end of the vane, andis not effective to urge the vane outwardly.

However, special provision is made for assuring contact of the cam sealing edge 70'of the vane with the cam surface as the vane moves from a zone of high pressure to a Zone of relatively low pressure. For this purpose, the structure of the vane defining thecam sealing edge is formed to slightly oilset the cam sealing edge from the plane of the distal side of the vane toward the proximal side of the vane.

As illustrated in FIG. 3, this is ac'hieved preferably by slightly rounding the corner or edge of the vane defining the cam sealing edge, to have a definite radius of curvature, which for clearness in illustration is greatly exaggerated in FIG. 3. It has been found that rounding of the corner of the vane defining the edge 70 to have a radius of curvature of 5,0Oths of an inch is satisfactory for this purpose. The effect of this is to displace or olfset the cam sealing edge 76 away from the plane of the distal side of the vane by a slight distance, identified in FIG. 3 by the number 94. i

The efiect of this is to reduce the fluid pressure force tending to move the vane radially inward in relation to the fluid pressure force tendingto move the vane outward, with the result that the vane is' held against the cam surface. Thus, the area at the outer end of the vane exposed to the higher fluid pressure covers a smaller projected area on a plane perpendicular to the direction of vane movement than doesthe area on the inner end of the vane which is exposed to the same higher fluid pressure. The effective end area of the outer end of the vane located at the distal side of the sealing edge 70 is, in this situation, exposed to a lower pressure and does not have the effect of neutralizing the outward force of the higher pressure fluid applied'to the differential areas which eiiect the outward biasing of the vane just described.

It will be understood be those skilled in the art that the features and concepts of this invention are not necessarily limited to use of the specific construction illustrated, but have a range of utility and adaptability within the spirit and scope of the invention as defined by the claims.

The invention is claimed as follows: i

1. In a hydraulicpower unit, the combination of a generally cylindrical rotor, a cam encircling said rotor, said rotor defining a plurality of circumferenttally spaced vane slots therein opening outwardly through the periphery of the rotor, each vane slot being defined by two parallel side surfaces, a plurality of vanes slidably mounted in, said respective slotsto continuously engage said cam, each vane being turned at an acute substantial angle relative to a radial line therethrough so that opposite side surfaces defining the slot and the corresponding sides of the coacting vane have a distal and proximal relationship respectively with respect to the axis of the rotor, each vane defining on the outer end thereof a cam engaging edge located adjacent the distal side of the vane, each vane having a thickness related to the angular orientation of the vane with respect to a radial line therethrough and to the maximum extension of the cam engaging edge of the vane beyond the periphery of the rotor which precludes projection of theproximal side of the vane beyond the proximal side surfaces of the coacting slot when the vane is in its fully extended position, each vane defining in the proximal side thereof a balancing cavity facing the proximal sidesurface of its slot, and being positioned on the vane so that the radially outer extremity of the cavity at the proximal side of the vane lies close to the corresponding outer extremity of the proximal side of the coacting vane slot when the vane is fully extended, said balancing cavity in each vane being continuously isolated from the bottom of the coact-. ing slot by engagement of a wide sealing surface on the vane with the proximal side surface of the slot and being continuously isolated from the interspace between the rotor and the cam at .the proximal side of the vane by engagement with the proximal side surface of the coacting slot of a narrow sealing edge formed on the vane between the cavity and the extreme outeredge of the proximal side of the vane, each vane being shaped to form a passage providing communication between said balancing cavity in the proximal sideof the vane and the interspace between the rotor and cam adjacent the distal side of the vane to provide a substantial balancing of pressure forces applied to the vane in directions perpendicular to the centnal plane of the coacting slot, and each vane being cavitated to provide continuous communication therethrough between the bottom of the coacting slot and the interspace between the cam and rotor at the proximal side of the vane while at the same time maintaining isolation of said balancing cavityin the vane from said interspace at the distal side of the vane.

2. In a hydraulic power unit, the combination of a generallycylindrical rotor, a. cam encircling said rotor, said rotor defining a plurality of circumferentially spaced vane slots therein opening outwardly through the periphery of the rotor, each vane slot being defined by two opposed side surfaces and being turned at a substantial angle to a radial line therethrough so that the side surfaces defining the slot have a distal and proximal relationship respectively with respect to the axis of the rotor, a pluraltiy of vanes slidably mounted in said respective slots to continuously engage said cam, each vane defining a cam engaging edge on the outer end thereof, each vane defining in the proximal side thereof a balancing cavity having an open face confronting the proximal side surface of its slot, said balancing cavity in each vane being positioned in relation to the vane so that upon movement of the vane to itsmost extended position the open face of the cavity at the proximal side of the vane is confronted over its entire extent by the proximal side surface of the coacting slot and the orthographic projection of said open face of the cavity on the plane of the distal side of the vane extends substantially beyond the periphery of the rotor, each vane being shaped andformed in relation to the coacting slot to continuously isolate the balancing cavity from the bottom of the coacting slot and from theinterspace between the cam and rotor adjacent the proximal side of the vane, each vane being shaped to form a passage providing communication between the balancing cavity in the vane and the interspace between the rotor and cam adjacent the distal side of the vane to effect a balancing of pressure forces applied to the vane in a direction perpendicular to the central plane of the coacting slot, and each vane defining a cavity positioned to provide continuous communication "between the bottom of the coacting slot and the interspace between the cam and rotor at the proximal side of the vane.

3. In a hydraulic power unit, the combination of a generally cylindrical rotor, a cam encircling said rotor, said rotor defining a plurality of circumferentially spaced vane slots therein opening outwardly through the periphcry of the rotorpa plurality of vanes slidably mounted in 7 said respective slots to continuously engage said cam, each vane slot being defined by two parallel side surfaces and being turned at a substantial angle relative to a radial line therethrough so that the side surfaces defining the slot and thecorresponding sides of the coacting vane have distal and proximal relationships respectively with respect to the axis of said rotor, each vane defining on the outer end thereof a cam engaging edge located adja'- cent the distal side of the vane, each vane defining in the proximal side thereof a balancing cavity having an open face confronting the proximal side surface of. the coacting slot, each vane defining sealing surfaces thereon engaging'the proximal side surface of the coacting slot to isolate the balancing cavity in each vane from the bottom of the coacting slot and from the interspace between the rotor and the cam at the proximal side of the vane; the thickness of each vane, the angle at which each vane slot is turned with reference to a radial line therethrough, and the position on each vane of said open face of the balancing cavity therein having a relationship to each other which causes the orthographic projection of said cavity face on the plane of the distal side of the vane to extend substantially beyond the periphery of the rotor when the vane is in its most extended position; each vane defining a passage connecting the balancing cavity in the vane with the interspace between the rotor and cam adjacent the distal side of the vane to provide a substantial balancing of pressure forces applied to the vane in a direction perpendicular to the central plane of the coacting slot, and each vane being shaped to define a passage'providing continuous communication between the bottom of the coacting slot and the interspace between the cam and rotor at the proximal side of the vane while .at the same time maintaining isolation of said balancing cavity in the vane from said interspace at the proximal side of the vane.

4.'In a hydraulic power unit, the combination of a rotor, means defining a cam surface encircling said rotor, said rotor defining a plurality of vane slots therein, a plurality ,of vanes slidably mounted in said respective slots to continuously engage said c-arn' surface, each of said slots being turned at -a substantial angle with respect to a radial line therethrough so that opposite sides of eachvane and the corresponding sides of the coacting slot have distal and proximal relationships respectively to the axis of the rotor, each vane defining a cam surface sealing edge positioned for slidable engagement with said cam surface, each vane defining in the proximal side thereof -a balancing cavity continuously confronting the proximal side of the coacting slot to define therewith a balancing interspace, said balancing cavity having a position on the vane such that the orthographic projection of the balancing cavity on the plane of the distal side of the vane extends beyond the rotor at the distal side ,of the coacting slot when the vane is in its fully extended position, each vane defining on the proximal side thereof a narrow sealing surface located between said balancing cavity and the outer end of the vane and positioned on the vane to continuously engage the proximal side of the coactingslot even when the vane is in its fully extended position to continuously isolate said balancing cavity from the interspace between said rotor and said cam surface at the proximal side of the vane, said narrow sealing surface on each vane extending beyond said sealing edge on the" vane with respect to the inner extremity of the vane, and each vane being shaped to form a passage for con necting said balancing cavity in the vane with the interspace between the rotor and cam surface adjacent the distal side of the vane to' effect a balancing of the lateral forces of fluid pressure on the vane.

5. In a hydraulic power unit, the combination of a cylindrical body, means defining a cam surface encircling said body, said body defining a plurality of circumferentially spaced vane slots therein, a plurality of vanes slidcavity spaces which coact with the corresponding sides of the coacting slot to define between the vane and the coacting slot distal andproximal vane balancing interspaces, said balancing cavity spaces in each vane being located in relation to the vane so, that the orthographic projection of the proximal cavity space on the plane of the distal side of the vane materially and continuously overlaps a similar projection of the distal cavity space in the vane and extends substantially beyond the periphery of said body at the distal side of the coacting slot when the vane is in its most extended position, each vane being shaped to form fiuid passage space connecting the distal and proximal cavity spaces in the vane, the distal side of each slot being shaped in relation to the coacting vane V to continuously provide communication between the adjacent cavity space in the vane and the interspace between said body and the'cam' surface adjacent the distal side of the vane even when the vane is in its fully retracted posi tion to effect a balancing of the lateral forces of pressure on the vane, and each vane including means for continuously isolating the balancing cavity spaces the vane from communication with the interspace between the cam surface and said body adjacent the proximal side ofthe vane.

6. In a hydraulic power unit, the combination of a rotor, means defining a cam surface encircling said rotor,

. of the slot and the corresponding sides of the vane therein have distal and proximal relationships respectively with respect to the axis of said rotor, each vane defining in the proximal side thereof a balancing cavity confronting the proximal side surface of the coacting slot to define therewith a vane balancing interspace; the thickness of each vane, the angle at which each vane slot is turned with "reference to a radial line through the center of the slot,

and the position on each vane of said balancing cavity therein having a relationship to each other which causes the. orthographic projection of the cavity on the plane of the distal side of the vane to extend substantially beyond the distal side of the slot when the vane is in its most extended position while the proximal side of the cavity isat the same time confined within the rotor so as to remain confronted over the entire extent of the proximal side of thecavity by the proximal side surface of the coacting slot; and each vane being shaped to form a passage connecting said balancing cavity therein with the interspace between said rotor "and said cam surface at the distal side of the vane when the vane is in an extended position. i

7. In a hydraulic power unit, the combination of a rotor, means defining 'a cam surface encircling said rotor,

said rotor defining a plurality of circumferentially spaced vane slots, a plurality of vanes slidably disposed in said with distal and proximal vane balancing interspaces, said balancing cavity spaces in each vane being located in relation to the vane so that the orthographic projection of the proximal cavity space on the plane of the distal side of the vane materially and continuously overlaps a similar projection of the distal cavity space in the vane and extends substantially beyond the periphery of said rotor at the distal side of the coacting slot when the vane is in its most extended position, each vane being shaped to form fluid passage space connecting the distal and proximal cavity spaces in the vane, said rotor and said vanes including means for continuously applying to the inner ends of said respective vanes the fluid pressure prevailing between said rotor and said cam surface at the proximal sides of the respective vanes, and means coacting with each vane to effect application to each vane of an outward force developed by fluid pressure which is at least equal to the pressure of fluid between said rotor and said cam surface at the distal side of the vane.

8. In a hydraulic power unit, the combination of a cylindrical body, means defining a cam surface encircling said body, said body defining a plurality of circumferentially spaced vane slots, a plurality of vanes slid-ably disposed in said respective slots to engage said cam surface, each of said slots being turned at a substantial angle with respect to a radial line through the center thereof so that opposite sides of each slot and the corresponding sides of the vane therein have distal and proximal relationships to the axis of said body, each vane being recessed on the distal and proximal sides thereof to define in the vane distal and proximal balancing cavity spaces which coact with the corresponding sides of the coacting slot to define therewith distal and proximal vane balancing interspaces, said balancing cavity spaces in each vane being located in relation to the vane so that the orthographic projection of the proximal cavity space on the plane of the distal side of the vane materially and continuously overlaps a similar projection of the distal cavity space in the vane and extends substantially beyond the periphery of said body at the distal side of the coacting slot when the vane is in its most extended position, and each vane being shaped to form fluid passage space connecting the distal and proximal cavity spaces in the vane.

9. In a hydraulic power unit, the combination of a rotor, means defining a cam surface encircling said rotor, said rotor defining a plurality of circumferentially spaced vane slots, a plurality of vanes slidably disposed in said respective slots, each of said vanes defining a cam sealing edge confronting said cam surface for engagement therewith, each of said slots being turned at a substantial angle with respect to a radial line through the center thereof so that opposite sides of each slot and the corresponding sides of the vane have distal and proximal relationships respectively to the axis of said body, said sealing edge on each vane being located adjacent the distal side of the vane in relation to the thickness of the vane between the proximal and distal sides thereof, each vane being recessed on the proximal side thereof to define in the vane a proximal balancing cavity which continuously confronts the proximal side of the coacting slot to define therewith a proximal vane balancing interspace, said balancing cavity in each vane having a position along the medial plane of the vane which is closely adjacent the position along said plane of said cam sealing edge on the vane, and each vane being shaped to form fluid passage space for connecting said proximal balancing cavity in the vane with the interspace between the rotor and cam surface at the distal side of the vane when the vane is extended.

10. In a hydraulic power unit, the combination of a rotor, means defining a cam surface encircling said rotor, said rotor defining a plurality of circumferentially spaced vane slots, a plurality of vanes slidably disposed in said respective slots, each of said vanes defining a sealing edge adapted to engage said cam surface, each of said slots being turned at a substantial angle with respect to a radial line through the center thereof so that opposite sides of each slot and the corresponding sides of the vane have distal and proximal relationships respectively to the axis of said body, said sealing edge on each v-ane being positioned proximate to the distal side of the vane in relation to the thickness of the vane between the proximal and distal sides thereof, each vane being recessed on the distal and proximal sides thereof to define in the vane distal and proximal balancing cavity spaces which coa'ct with the corresponding sides of the coacting slot to define therewith :distal and'proxim'al vane balancing interspaces, said distal and proximal cavity spaces in each vane being located in relation to the vane so that the positions of the distal and proximal cavity spaces along the medial plane of the vane are closely adjacent the position along the same plane of said sealing edge, and each vane being shaped to form fluid passage space connecting the distal and proximal cavity spaces in the vane.

References Cited in the file of this patent UNITED STATES PATENTS 1,692,473 Smith Nov.. 20, 1928 2,545,238 MacMillan et al Mar. 13, 1951 2,764,941 Miller et a1 Oct. 2, 1956 2,949,081 Deschamps Aug. 16, 1960 2,967,488 Gardiner Jan. 10, 1961 2,967,489 Harrington Ian. 10, 1961 FOREIGN PATENTS 142,833 Switzerland Dec. 16, 1930 471,852 Germany Feb. 15, 1929 606,413 Great Britain Aug. 12, 194-8 

1. IN A HYDRAULIC POWER UNIT, THE COMBINATION OF A GENERALLY CYLINDRICAL ROTOR, A CAM ENCIRCLING SAID ROTOR, SAID ROTOR DEFINING A PLURALITY OF CIRCUMFERENTIALLY SPACED VANE SLOTS THEREIN OPENING OUTWARDLY THROUGH THE PERIPHERY OF THE ROTOR, EACH VANE SLOT BEING DEFINED BY TWO PARALLEL SIDE SURFACES, A PLURALITY OF VANES SLIDABLY MOUNTED IN SAID RESPECTIVE SLOTS TO CONTINUOUSLY ENGAGE SAID CAM, EACH VANE BEING TURNED AT AN ACUTE SUBSTANTIAL ANGLE RELATIVE TO A RADIAL LINE THERETHROUGH SO THAT OPPOSITE SIDE SURFACES DEFINING THE SLOT AND THE CORRESPONDING SIDES OF THE COACTING VANE HAVE A DISTAL AND PROXIMAL RELATIONSHIP RESPECTIVELY WITH RESPECT TO THE AXIS OF THE ROTOR, EACH VANE DEFINING ON THE OUTER END THEREOF A CAM ENGAGING EDGE LOCATED ADJACENT THE DISTAL SIDE OF THE VANE, EACH VANE HAVING A THICKNESS RELATED TO THE ANGULAR ORIENTATION OF THE VANE WITH RESPECT TO A RADIAL LINE THERETHROUGH AND TO THE MAXIMUM EXTENSION OF THE CAM ENGAGING EDGE OF THE VANE BEYOND THE PERIPHERY OF THE ROTOR WHICH PRECLUDES PROJECTION OF THE PROXIMAL SIDE OF THE VANE BEYOND THE PROXIMAL SIDE SURFACES OF THE COACTING SLOT WHEN THE VANE IS IN ITS FULLY EXTENDED POSITION, EACH VANE DEFINING IN THE PROXIMAL SIDE THEREOF A BALANCING CAVITY FACING THE PROXIMAL SIDE SURFACE OF ITS SLOT, AND BEING POSITIONED ON THE VANE SO THAT THE RADIALLY OUTER EXTREMITY OF THE CAVITY AT THE PROXIMAL SIDE OF THE VANE LIES CLOSE TO THE CORRESPONDING OUTER EXTREMITY OF THE 